Thrombosis is one of the major problems of modern man and research directed to its control is a major health goal. The proposed program is designed to establish an interdisciplinary Thrombosis SCOR at Cornell University Medical College. The activity represents the combined interrelated efforts of nine major laboratories all working on the fundamental biochemical and physiological background of the human thrombotic process. The long term aim of the program is to clarify and define Thrombogenesis in meaningful clinical terms which may have eventual therapeutic relevance in man. An underlying theme which serves as a common denominator of the individual projects is the recognition and definition of the basic cellular and biochemical determinants of the thrombotic process. The coordinated interrelationships of platelets, endothelial cells and circulating protease inhibitors as important denominators of localized events will be stressed. The supplemental request is to allow the continuation of two currently ongoing projects (1) Platelet-Blood Vessel Wall Interactions in Thrombosis: Platelet and Leukocyte Inflammatory Factors and their Regulation-Project IX-under the direction of Enrique Rabellino. In addition supplemental funds are being requested to expand two projects (1) Ultrastructural Studies of Membrane Changes in Platelet Physiology with Particular Reference to the Role of Complement-Project IV-under the direction of Margaret Polley (2) Etiology and Pathogenesis of Atherosclerosis-Project VI-under the direction of Carl Becker.